Stainless Steel CF20-AC vs CF20-ST
Stainless Steel · CF20 temper comparison
CF20-AC and CF20-ST are two conditions of the same stainless steel grade, CF20: AC (spheroidize annealed) versus ST (solution annealed). The chemistry is identical, so every difference below comes from the condition. CF20-AC is the stronger of the two: yield strength 275 MPa (39.9 ksi) against 255 MPa (37 ksi) for CF20-ST, about 8% more. In exchange, CF20-ST is the more ductile: elongation 38% versus 22% for CF20-AC, and CF20-AC is harder (175 HB vs 156 HB). On the shop floor, CF20-ST welds better (good vs fair).
CF20-ACChoose it when strength drives the design.
CF20-STChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
CF20-AC vs CF20-ST: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all stainless steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 193 GPa28 Msi · Shear Modulus 75 GPa10.9 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Same in both: Density 7.75 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 16.2 W/m·K9.4 BTU/hr·ft·°F · Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 17.2 µm/m·K9.6 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -100°C-148 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Same in both: Electrical Conductivity 2.4 % IACS
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.08 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 78 / 100 · Brazeability / Solderability 55 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 53 MJ/kg22,786 BTU/lb · Embodied Carbon (primary production) 4.6 kg CO₂/kg · Embodied Water 130 L/kg15.6 gal/lb · Typical Recycled Content 80%
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
CF20-AC vs CF20-ST — frequently asked
Is CF20-AC stronger than CF20-ST?
Yes. CF20-AC has a typical yield strength of 275 MPa (39.9 ksi) against 255 MPa (37 ksi) for CF20-ST — about 8% more. Tensile strength is 520 MPa (75.4 ksi) vs 530 MPa (76.9 ksi).
Which condition does FabDigit quote by default, AC or ST?
ST is the default CF20 condition in the FabDigit quote flow. The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, CF20-AC or CF20-ST?
CF20-ST. Its machinability rates fair (38/100) against poor (33/100) for CF20-AC; for welding the order is CF20-ST first (good, 55/100) then CF20-AC (fair, 40/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CF20-AC and CF20-ST side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.